Prevalence of Simple Nodular Goiter and Hashimoto's Thyroiditis in Current, Previous, and Never Smokers in a Geographical Area with Mild Iodine Deficiency

Simple nodular goiter and Hashimoto's thyroiditis are 2 frequent nonmalignant thyroid diseases. Tobacco smoking has detrimental effects on the endocrine system and in particular on thyroid function and morphology. The objective of this cross-sectional study, involving 1800 Caucasian adults from a geographical area with mild iodine deficiency, was to evaluate the relationship between tobacco smoking, smoking cessation, and the prevalence of simple nodular goiter and Hashimoto's thyroiditis. Thyroid status was evaluated by ultrasonic exploration of the neck, measurement of FT3, FT4, TSH, antibodies against thyroid peroxidase and thyroglobulin, and urinary iodine excretion. The fine-needle aspiration biopsy of significant nodules was also performed. Smoking habits were evaluated by a specific questionnaire and the calculation of number of pack years. Both current and previous smokers showed an increased risk of simple nodular goiter compared to never smokers after adjustment for potential confounders and known goitrogen factors. Interestingly, the simple nodular goiter risk was similar for never smokers and for previous smokers declaring a time since cessation of smoking for more than 69 months. Smoking habit was not associated to an increased risk of Hashimoto's thyroiditis. Smoking appears to be an independent risk factor for simple nodular goiter but not for Hashimoto's thyroiditis in an area with mild iodine deficiency. A prolonged withdrawal of smoking dramatically reduces the risk of simple nodular goiter occurrence.